PROVE Primary Battery Structure

In conjunction with Prototype Vehicle (PROVE) Laboratory, our group designed, manufactured, and tested a prototype structure to house the battery boxes for PROVE’s endurance vehicle. Our structure was designed to support the batteries during normal use, and in the event of a front crash. Our design is comprised of a secondary composite box to house the battery boxes, a bottom plate to affix the secondary box to the chassis floor, a horizontal plate fastened to the chassis, and a brace structure welded to the chassis. From the outset, we chose to use a secondary box, the primary battery boxes must be removable, and we could not directly affix supports. In areas of less certainty, such as the number of support or the strength of support methods, we initially used intuition to make decisions, and allowed room for iteration once we had sufficient analysis later in the project. After developing our initial structure, we created FEM case studies on the full assembly, and used hand calculations to verify our FEM. We were most concerned with the deflection of the front wall in a front 20g crash. We used laminate plate theory in a python algorithm to verify FEM results for the front wall deflection. We found that the brace structure failed in the FEM study. However, we also anticipate redesigning or possibly removing the brace in favor of an additional plate joining the chassis tubes parallel to the front wall. Our team manufactured layups of carbon fiber sandwich panels and L channels for the secondary structure and bottom plate. We successfully integrated the bottom plate and secondary box. However, due to tolerancing issues and discrepancies between the CAD and the physical vehicle our brace structure requires alteration to be integrated. Threaded inserts were manufactured on a lathe and bonded into the panels to allow for them to be integrated onto the chassis. The secondary structure was manufactured smoothly and could fit onto the chassis, which is a great success. One of the two horizontal plates and braces were water jetted and welded respectively, but they need to be redesigned to properly suit their integration. Additionally, our team characterized the Elastic moduli and Poisson’s ratio of carbon fiber material using tensile and strain gauge testing

Low-Mach-number turbulence in interstellar gas revealed by radio polarization gradients

The interstellar medium of the Milky Way is multi-phase, magnetized and turbulent. Turbulence in the interstellar medium produces a global cascade of random gas motions, spanning scales ranging from 100 parsecs to 1000 kilometres. Fundamental parameters of interstellar turbulence such as the sonic Mach number (the speed of sound) have been difficult to determine because observations have lacked the sensitivity and resolution to directly image the small-scale structure associated with turbulent motion. Observations of linear polarization and Faraday rotation in radio emission from the Milky Way have identified unusual polarized structures that often have no counterparts in the total radiation intensity or at other wavelengths, and whose physical significance has been unclear. Here we report that the gradient of the Stokes vector (Q,U), where Q and U are parameters describing the polarization state of radiation, provides an image of magnetized turbulence in diffuse ionized gas, manifested as a complex filamentary web of discontinuities in gas density and magnetic field. Through comparison with simulations, we demonstrate that turbulence in the warm ionized medium has a relatively low sonic Mach number, M_s <~ 2. The development of statistical tools for the analysis of polarization gradients will allow accurate determinations of the Mach number, Reynolds number and magnetic field strength in interstellar turbulence over a wide range of conditions.Comment: 5 pages, 3 figures, published in Nature on 13 Oct 201

Experience With the Cardiac Surgery Simulation Curriculum: Results of the Resident and Faculty Survey

BACKGROUND: The Cardiac Surgery Simulation Curriculum was developed at 8 institutions from 2010 to 2013. A total of 27 residents were trained by 18 faculty members. A survey was conducted to gain insight into the initial experience. METHODS: Residents and faculty were sent a 72- and 68-question survey, respectively. In addition to demographic information, participants reported their view of the overall impact of the curriculum. Focused investigation into each of the 6 modules was obtained. Participants evaluated the value of the specific simulators used. Institutional biases regarding implementation of the curriculum were evaluated. RESULTS: Twenty (74%) residents and 14 (78%) faculty responded. The majority (70%) of residents completed this training in their first and second year of traditional-track programs. The modules were well regarded with no respondents having an unfavorable view. Both residents and faculty found low, moderate, and high fidelity simulators to be extremely useful, with particular emphasis on utility of high fidelity components. The vast majority of residents (85%) and faculty (100%) felt more comfortable in the resident skill set and performance in the operating room. Simulation of rare adverse events allowed for development of multidisciplinary teams to address them. At most institutions, the conduct of this curriculum took precedence over clinical obligations (64%). CONCLUSIONS: The Cardiac Surgery Simulation Curriculum was implemented with robust adoption among the investigating centers. Both residents and faculty viewed the modules favorably. Using this curriculum, participants indicated an improvement in resident technical skills and were enthusiastic about training in adverse events and crisis management

JWST Constraints on the UV Luminosity Density at Cosmic Dawn: Implications for 21 cm Cosmology

An unprecedented array of new observational capabilities are starting to yield key constraints on models of the epoch of first light in the Universe. In this Letter we discuss the implications of the UV radiation background at cosmic dawn inferred by recent JWST observations for radio experiments aimed at detecting the redshifted 21 cm hyperfine transition of diffuse neutral hydrogen. Under the basic assumption that the 21 cm signal is activated by the Lyα photon field produced by metal-poor stellar systems, we show that a detection at the low frequencies of the EDGES and SARAS3 experiments may be expected from a simple extrapolation of the declining UV luminosity density inferred at z ≲ 14 from JWST early galaxy data. Accounting for an early radiation excess above the cosmic microwave background suggests a shallower or flat evolution to simultaneously reproduce low- and high-z current UV luminosity density constraints, which cannot be entirely ruled out, given the large uncertainties from cosmic variance and the faint-end slope of the galaxy luminosity function at cosmic dawn. Our findings raise the intriguing possibility that a high star formation efficiency at early times may trigger the onset of intense Lyα emission at redshift z ≲ 20 and produce a cosmic 21 cm absorption signal 200 Myr after the Big Bang

Simulation-Based Training in Cardiac Surgery

BACKGROUND: Operating room surgical training has significant limitations. This study hypothesized that some skills could be learned efficiently and safely by using simulation with component task training, deliberate practice, progressive complexity, and experienced coaching to produce safer cardiac surgeons. METHODS: Training modules included cardiopulmonary bypass, coronary artery bypass grafting, aortic valve replacement, massive air embolism, acute intraoperative aortic dissection, and sudden deterioration in cardiac function. Using deliberate practice, first-year cardiothoracic surgical residents at eight institutions were trained and evaluated on component tasks for each module and later on full cardiac operations. Evaluations were based on five-point Likert-scale tools indexed by module, session, task items, and repetitions. Statistical analyses relied on generalized linear model estimation and corresponding confidence intervals. RESULTS: The 27 residents who participated demonstrated improvement with practice repetitions resulting in excellent final scores per module (mean ± two SEs): cardiopulmonary bypass, 4.80 ± 0.12; coronary artery bypass grafting, 4.41 ± 0.19; aortic valve replacement, 4.51 ± 0.20; massive air embolism, 0.68 ± 0.14; acute intraoperative aortic dissection, 4.52 ± 0.17; and sudden deterioration in cardiac function, 4.76 ± 0.16. The transient detrimental effect of time away from training was also evident. CONCLUSIONS: Overall performance in component tasks and complete cardiac surgical procedures improved during simulation-based training. Simulation-based training imparts skill sets for management of adverse events and can help produce safer surgeons

Size-resolved mixing state of black carbon in the Canadian high Arctic and implications for simulated direct radiative effect

Transport of anthropogenic aerosol into the Arc- tic in the spring months has the potential to affect regional climate; however, modeling estimates of the aerosol direct radiative effect (DRE) are sensitive to uncertainties in the mixing state of black carbon (BC). A common approach in previous modeling studies is to assume an entirely exter- nal mixture (all primarily scattering species are in separate particles from BC) or internal mixture (all primarily scat- tering species are mixed in the same particles as BC). To provide constraints on the size-resolved mixing state of BC, we use airborne single-particle soot photometer (SP2) and ultrahigh-sensitivity aerosol spectrometer (UHSAS) mea- surements from the Alfred Wegener Institute (AWI) Polar 6 flights from the NETCARE/PAMARCMIP2015 campaign to estimate coating thickness as a function of refractory BC (rBC) core diameter and the fraction of particles contain- ing rBC in the springtime Canadian high Arctic. For rBC core diameters in the range of 140 to 220 nm, we find av- erage coating thicknesses of approximately 45 to 40 nm, re- spectively, resulting in ratios of total particle diameter to rBC core diameters ranging from 1.6 to 1.4. For total par- ticle diameters ranging from 175 to 730 nm, rBC-containing particle number fractions range from 16% to 3%, respec- tively. We combine the observed mixing-state constraints with simulated size-resolved aerosol mass and number dis- tributions from GEOS-Chem–TOMAS to estimate the DRE with observed bounds on mixing state as opposed to assuming an entirely external or internal mixture. We find that the pan-Arctic average springtime DRE ranges fro

Influence of mitral valve repair versus replacement on the development of late functional tricuspid regurgitation

ObjectivesTo study the determinants of functional tricuspid regurgitation (TR) progression after surgical correction of mitral regurgitation, including the influence of mitral valve (MV) repair (MVr) versus replacement (MVR) for degenerative mitral regurgitation.MethodsFrom January 1995 to January 2006, 747 adults with MV prolapse underwent isolated MVr (n = 683) or MVR (n = 64; mechanical in 32). The mean age was 60.8 years, and 491 were men (66.0%). Moderate preoperative functional TR was present in 115 (15.4%). The MVR group had a greater likelihood of New York Heart Association class III or IV (75.0% vs 34.4%, P < .001), atrial fibrillation (20.3% vs 8.3%, P = .002), a lower left ventricular ejection fraction (61.0% vs 65.2%, P < .003), and a higher pulmonary artery pressure (50.1 vs 41.2 mm Hg, P = .001). The patients were monitored for a mean of 6.9 years (MVr) or 7.7 years (MVR; P = .075).ResultsDuring late follow-up, no difference was found between the groups in the development of moderately severe or severe TR: 1 to 5 years (3.0% vs 3.3%, P = .91) and >5 years (6.1% vs 6.5%; P = .93). The univariate predictors of severe TR after 5 years were older age (hazard ratio [HR], 1.1; P = .011), female gender (HR, 6.86; P = .005), higher pulmonary artery pressure (HR, 1.05; P = .022), and larger left atrial size (HR, 2.11; P = .035). Two patients (0.26%) who had undergone initial MVr required reoperation for late functional TR. Another 2 patients had had the tricuspid valve addressed concurrent with reoperation for MVr failure. No tricuspid reoperations were required in the MVR group.ConclusionsThe risk of TR progression was low after MVr or MVR for MV prolapse. Timely MV surgery before the development of left atrial dilatation or pulmonary hypertension could further decrease the risk of TR progression during follow-up